Improved bis(hydroxyalkyl) styryl dye compounds and photosensitive media containing such compounds

ABSTRACT

This invention relates to an improved process for the preparation of organic dyestuffs and especially styryl dyes which are particularly useful in improving the photographic exposure speed of reproduction systems. The process involves the condensation of a color former with a Schiff&#39;&#39;s base, the color former and Schiff&#39;&#39;s base being selected to provide the desired dyestuff. For the styryl dyes, the color former is a heterocyclic aromatic compound and the Schiff&#39;&#39;s base is of an aminosubstituted aromatic aldehyde. The heterocyclic compound contains at least one quaternary nitrogen hetero atom and at least one methyl group as a ring substituent. The present process provides a more efficient and practical method of producing the styryl dyes than the prior art method in which the aldehyde corresponding to the Schiff&#39;&#39;s base is utilized as condensing agent, the resulting overall yields being substantially higher. This invention also relates to a new series of compounds which are characterized by having at least one hydroxyalkyl substituent on the amino substituent of the styryl dye. These compounds give greater photograhic exposure speed than otherwise equivalent styryl dyes which lack a hydroxyalkyl group on the amino substituent.

United States Patent 1191 Keller IMPROVED BIS(HYDROXYALKYL) STYRYL DYECOMPOUNDS AND PHOTOSENSITIVE MEDIA CONTAINING SUCH COMPOUNDS Juergen H.H. Keller, Chelmsford, Mass.

[73] Assignee: Itek Corporation, Lexington, Mass.

22 Filed: Feb. 3, 1969 [2]] Appl. No.: 796,167

[ 75] Inventor:

OTHER PUBLICATIONS Katayanagi, J. Pharm. Soc, Japan, vol. 68, pages228-3 (1948). Katayanagi, Chemical 4545-4546 (1954). Hamer, The CyanineDyes and Related Compounds, (abstract of above Katayanagi article),pages 410-4l l, lnterscience Publishers (1964). Hamer, The Cyanine Dyesand Related Compounds,

Abstracts, vol. 48, cols.

pages 4l3-4l5, added, lnterscience Publishers (1964).

Primary Examiner.lohn D. Randolph Attorney, Agent, or Firm-Homer 0,Blair; Robert L. Nathans; W. Gary Goodson 5 7 ABSTRACT This inventionrelates to an improved process for the preparation of organic dyestuffsand especially styryl dyes which are particularly useful in improvingthe photographic exposure speed of reproduction systems. The processinvolves the condensation of a color former with a Schiffs base, thecolor former and Schiffs base being selected to provide the desireddyestuff. For the styryl dyes, the color former is a heterocyclicaromatic compound and the Schiffs base is of an amino-substitutedaromatic aldehyde. The heterocyclic compound contains at least onequaternary nitrogen hetero atom and at least one methyl group as a ringsubstituent. The present process provides a more efficient and practicalmethod of producing the styryl dyes than the prior art method in whichthe aldehyde corresponding to the Schiffs base is utilized as condensingagent, the resulting overall yields being sub-, stantially higher.

5 Claims, N0 Drawings IMPROVED BIS(I-IYDROXYALKYL) STYRYL DY COMPOUNDSAND PHOTOSENSITIVE MEDIA CONTAINING SUCH COMPOUNDS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to theprocess of preparing organic dyes and particularly styryl dyes, as wellas new styryl dyes which are especially effective in sensitizingphotographic media to visible light.

2. Description of the Prior Art The condensation of an aldehyde with acolor former to produce organic dyes is a well-known reaction, usuallyinvolving carbonyl condensation with an active methylene group of thecolor former to yield an ethylenic linkage.

The hemicyanine dyes are well-known compounds which are characterized byat least two amino nitrogen atoms connected by a chain of conjugateddouble bonds, with one of the nitrogen atoms being part of aheterocyclic nucleus, the other being an amino substituent on abenzenoid nucleus, the latter being connected to'the heterocyclicnucleus by an unsaturated chain of carbon atoms, the double bonds ofwhich are conjugated with the said nuclei. The simplest of thesecompounds arethose in which the unsaturated chain is an ethylene group,i.e., the styryl dyes.

The styryl dyes are well-known and have been described in innumerableliterature articles and standard texts (vide: Cyanine Dyes and RelatedCompounds, Hamer (1964) lnterscience Publishers, John Wiley & Sons, NewYork, N.Y.).

The usual method of preparing the said dyes is by condensation of anamino-substituted benzaldehyde with a heterocyclic compound containingat least one quaternary nitrogen hetero atom and an active methylsubstituent. For example, pdimethylaminobenzaldehyde condenses with-picoline methiodide to form the corresponding styryl dye. The

condensation reaction is catalysed by the presence of an amine, usuallypiperidine.

The usual method of preparation of the paminobenzaldehyde intermediateinvolves condensation of a p-nitrosoaniline with an aniline compound toform the corresponding Schiffs base, in the presence of formaldehyde,followed by hydrolysis to the corresponding aminobenzaldehyde. Thehydrolysis reaction is not always efficient as far as yields of thedesired endproduct is concerned.

A particularly effective group of hemicyanine dyes and the method of useas photographic sensitizers is described in a commonly assigned,copending US. Pat, application, Ser. No. 633,689, now US. Pat. No.3,666,464 granted May 30, 1972 filed Apr. 26, [967 which is incorporatedherein by reference.

SUMMARY OF THE INVENTION It has now been discovered that the process ofpreparing organic dyes, especially styryl dyes, is substantiallyimproved by substitution of a Schiffs base for the aldehyde employed inthe condensation with the active methyl group, as hereinbeforedescribed. It is indeed surprising that the Schiffs base will functionin the said condensation reaction and, as a result, substantiallyimproved overall yields of the final styryl product are obtained. Forexample, in the preparation of the N- hydroxyalkyl substituted styryldyes, as described herein, the overall yields of products are improvedup' to four-fold and sometimes higher, when compared to the aforesaidmethod of preparation based on use of the corresponding aldehyde. I

It is thought that the free aldehyde grouping undergoes competingreactions and thus leads to reduced overall yields. The correspondingSchiffs base, on the other hand, does not appear to react in thesesecondary or competing reactions or at least the extent to which suchsecondary reactions occur is minimized in comparison to the freealdehyde. Whatever the explanation, it remains that the use of thecorresponding Schiffs base leads to substantial improvement in the saidprocess.

The present method can also be employed and is especiallyeffective inthe parparation of a new class of styryl dyes which are particularlyeffective in improving the photographic speed of media described herein.The specific new styryl compounds are those in which at least one of R,and R of the substituent, -NR,R is a hydroxyalkyl substituent.Especially preferred compounds are those in which both R, and R are eachbydroxyalkyl. Such hydroxyalkyl compounds give increased speeds incomparison with corresponding compounds in which R, and R are other thanhydroxyalkyl, the increase in speed amounting to an average of two tothree fold, in general.

The new compounds which are useful in the same manner as the knownstyryl dyes are represented by the formula:

DESCRIPTION OF PREFERRED EMBODIMENTS The preferred new compounds arethose in which Y is one of the following formulae:

Formula I 8 iii Rex

Formula II R;

NRa \g,/

Formula III Formula IV R- Ra I i J- l RQX Formula V R A N l l RQX' andFormula VI R5 RQX' wherein A is oxygen, sulfur or selenium; R is alkoxyor amino, especially diakylamino; R is hydrogen, alkyl, aralkyl orhydroxyalkyl; R and R are as previously described; and X is a negativeradical, such as halide radical, e.g., chloride, bromide, iodide orfluoride ion, derived from the quaternary ammonium salt former. Suchnegative radicals'can include any of the negative ions of acids whichform salts with the amino nitrogen of the heterocyclic ring; oralternatively from alkyl sulfates, nitrates or the like. The preferred Rsubstituent is hydroxyalkyl.

In the foregoing description of the new compounds of this invention, thevarious hydrocarbon substituents preferably contain not more than 8carbon atoms and the alkyl substituents, including hydroxyalkyl, arelower alkyl, e.g., contain from l to about 5 carbon atoms.

The concentration of the present new compounds in their use inphotographic media as well as the details of their incorporation intothe media is the same as with similar compounds of the prior art and theaforesaid copending U.S. application, Ser. No. 633,689, now US. Pat. No.3,666,464 provides full details thereof.

The present new compounds are prepared by the present new and improvedprocess using the Schiffs base or by the art-recognized processes, e.g.by condensing the corresponding aldehyde with a suitable heterocycliccompound, as described, with the overall yields of the latter processbeing substantially lower. As is quite apparent, the synthesis of thesaid aldehyde involves the production of a Schiffs base which is thenconverted to the free aldehyde. Thus the use of the Schiffs baseobviates the step of conversion to the free aldehyde. thus leading to amore efficient process and higher overall yields since the saidconversion usually leads to low yields of the aldehyde. However, it isfurther apparent from the results observed that the condensation of theSchiff's base with the selected heterocyclic compound is more efficientthan the same condensation of the free aldehyde. In the condensationwith free aldehyde. there appears to be substantial competing reactionswhich lead to mixtures of products, with the desired product not alwaysbeing the major constituent. Due to such mixtures, the desired productis only obtainable by expensive and timeconsuming separation procedures,e.g., chromatography ad selective crystallization solvents. When theSchiffs base is used, such problems are usually avoided, or at leastminimized since simple recovery techniques seem to be sufficient toobtain the end product, i.e., if the product obtained is a mixture, thedesired end product is the major constituent and readily recoverable.

The present new process is particularly effective in the preparation ofthe present new compounds contain- 5 ing a hydroxyalkyl substitutedamino group, where the best improvement in yields is realized. 1 In thepresent new process, the preferred Schiffs base is of the formula:

0 in which each R and R are each hydrogen, alkyl, aryl,

aralkyl, alkaryl and especiallyv hydroxyalkyl, particularly in which thealkyl moiety is lower alkyl. The preferred heterocyclic aromaticcompounds are those containing at least one nitrogen hetero atom and atleast 15 one methyl group as a ring substituent. Such heterocycliccompounds may also contain additional inert substituents, i.e., thosewhich do not adversely affect the condensation reaction, e.g.,hydrocarbon substituents such as alkyl, aryl, aralkyl, alkaryl,cycloalkyl, alkenyl and the like, which may be substituted by suchgroups as hydroxy, amino, halo, alkoxy and the like; and substituentssuch as halogen, hydroxy, cyano, alkoxy, amino, etc. The heterocyclicring can also be a condensed ring system, i'.e., condensed with benzeneor naphthalene ring systems.

The preferred color formers are heterocyclic ring systems such asthiazole, quinoline, thiadiazole, benzimidazole, benzothiazole andindole ring systems. For

reaction to produce an ethylenic group, the color forpicted, forexample, in formula l-Vl. The following examples further illustrate theherein described inven-.

, tion.

EXAMPLE 1 A. Preparation of Schiffs base:

A mixture of bis (B-hydroxyethyl) aniline (72.4g.), ml. of water and 80ml. of cone. HCl is stirred in a flask and cooled to 5C. A solution of29.2g. NaNO in ml. H O is added over a period of 40 minutes while thetemperature is maintained at 5C. The mixture is then filtered and thesolid washed with ml. of dilute HCl to obtain 92g. of wet orangematerial which is added to a solution, prepared by heating on a steambath bis (B-hydroxyethyl) aniline ml conc. HCl 50 ml 37 percent aqueousformaldehyde The reaction mixture is allowed to stand for one hourand'800 g. of crushed ice is added and followed by neu- 5 tralizing with40 percent NaOH solution. A plastic mass forms and is separated andwashed several times with cold water. The mass is crystallized fromethanol to obtain 67 g. of product, m. l77l78C., N-[pbis(hydroxyethyl)aminobenzylidine]p-[bis(hydroxyethyl)amino] aniline.

B. Preparation of aldehyde A mixture of 54 g. of the Schiffs base thusobtained, 84 ml. acetic acid and 40 ml of 37 percent aqueousformaldehyde is stirred at room temperature for four hours. The mixtureis then cooled, diluted with ml. of ice water, then made alkaline withammonium hydroxide and extracted with 10 portions of boiling chloroform3000 ml. total volume). The combined chloroform extracts are dried overanhydrous magnesium sulfate and then evaporated to obtain 25 g. ofsticky yellow product.

C. 4-Phenyl-2[p-bis( B-hydroxyethyl)aminostyryl]thiazole-3-B-hydroxyethobromide.

2-Methyl-4-phenylthiazole (9g.) and bromoethanol (7g) are heated for 4hours at 1 15C., cooled, slurred with ether, filtered, washed with etherand dried to obtain 3g. of the hydroxyethobromide.

The hydroxyethobromide salt (3g) and the Schiffs base of paragraph A(4g) are refluxed in 40 ml. ethanol containing piperidine (lg.) for 15minutes. After cooling acetone and ether is added to precipitate asticky product, 6.5 g. of crude product whichis then stirredsuccessively with 5 portions of acetone to obtain 4.3g. of product.Recrystallization from hot methanol by addition of acetone (two times)gives the product, m. 187l88C. (D-max. 0.9 at 492 millimicronsl/l 10,000methanol).

This product is converted to the chloride by dissolving in boiling water(1.2g/20O ml.) and adding 30g. NaCl. The mixture is cooled and filteredto obtain 1.0g.

of the chloride. Recrystallization from ethanol gives a product whichmelts at 217-218C., Dmax. 0.98 at 492 millimicrons (l/l 10,000methanol).

EXAMPLE 2 ml. ofacetone. After one hour of cooling in the freezer, v

the material is filtered, washed with alcohol and acetone and dried.After one recrystallization from methanol, 54g. of dye are obtained.Recrystallization from ethanol gives a product which melts at 227228C,Dmax. 0.86 at 482 ml. (l/1l0,000 methanol); yield 50.5 percent (based onquaternary salt).

Aldehyde Method: 2,4-Dimethylthiazole hydroxyethobromide (4.8g)

' and p-bis (B-hydroxyethyl) aminobenzaldehyde (4.2g.)

in 10 ml. ethanol containing 1.5g. piperidine are refluxed for minutes.After cooling, the addition of acetone gave a light purple material(2.2g), Dmax. 0.69;

The procedure of paragraph C of Example 1 is repeated using thefollowing heterocyclic compounds to obtain the corresponding dye:

after recrystallization from ethanol, Dmax. 0.82, 482 millimicrons,l/ll0,000 methanol, in. 227-228C., yie1d=l.2g. (13.9 percent based onthe weight of the quaternary salt).

EXAMPLE 5 6-Dimethylaminoquinaldine-B-hydroxyethobromide (6.2g) andp-bis (,B-hydroxyethyl) aminobenzaldehyde (4.2g.) in 15 ml. of ethanolcontaining 1.5g piperidine is refluxed for 5 minutes and 20 ml. ofethanol then Absorption Peak of Resulting Dye (in milli- HeterocyclicCompound microns) I lepidine hydroxyethobromide quinaldinemetho-mcthylsulfate EXAMPLE 32-[p-bis(B-Hydroxyethyl)aminostyryl]-5-methyl- 1,3,4-thiadiazole-3-,8-hydroxyethobromide 2,5-Dimethyl-1,3,4-thiadiazole(g) is heated to l 10C. and 52.5g. of bromoethanol added over a periodof 35 minutes at 110C. and heating is continued for 15 minutes at 110C.After cooling, acetone is added and the product washed several timeswith acetone to obtain g. of the ethobromide salt.

The ethobromide salt'( 12g), the Schiffs base from Example 1 (19.5g.) in50 ml. of ethanol containing 4.4g. piperidine is heated to refluxtemperature, then cooled and diluted with acetone. The precipitatedproduct is filtered to obtain 16g. of purple crystals, afterrecrystallization from methanol, Dmax. 1.14, 498 millimicrons, 1/110,000 methanol.

EXAMPLE 4 4-methyl-2-[pbis( hydroxyethyl )aminostyryl]thiazole-B-hydroxyethobromide Schiff's Method:

EXAMPLE 6 The Example 4 product is converted to the correspondingchloride by refluxing in a mixture of silver chloride (freshly prepared)in methanol for 4 hours. The mixture is filtered and the filtrateconcentrated to precipitate the chloride salt, Dmax. 0.97, 480millimicrons (l/l 10,000 methanol) m. 231-232C. after recrystallizationfrom ethanol.

EXAMPLE 7 The Example 5 product is converted to the correspondingchloride by the method of Example 6. The

product is recrystallized from ethanol, m. 249-250C., Dmax. 1.08, 534millimicrons (l/l 10,000 methanol).

PHOTOGRAPHlC SPEED DETERMINATION A mixture of 4 parts by weight oftitanium dioxide and 1 part by weight of an emulsion of Rhoplex acrylateresin containing about 50 per cent of solids in water is used to coatpaper sheets.

A sheet of the coated paper is sensitized by dipping into a solutioncontaining 20 milligrams of the selected dye(2-p-dimethylaminostyryl-4-methylthiazole metho chloride) in 200 ml. ofmethanol, and then dried.

The sensitized paper is exposed to imaging light from a Kodak I01sensitometer which has a tungsten lamp producing an intensity of I700meter candles at the sensitometric wedge and a color temperature of2650K for twenty seconds.

The exposed prints are then dipped in a saturated solution of silvernitrate in methanol, and than in a solution comprising 5 gm ofphenidone, 40 gm. of citric acid monohydrate, and 1 liter of methanol. Avisible negative image of the positive exposure image was obtained. Thevisible image bearing print is then immersed in a methanolic potassiumthiocyanate (KSCN) stop bath, then fixed by immersing in an aqueoussodium thiosulfate solution, and finally washed in running water. Thephotographic speed was determined by the LES method. LES (abbreviationfor light exposure speed) refers to a speed rating system developed atthe Wright Air Development Division of the Air Research and DevelopmentCommand (U.S.A.F.), and is defined as the reciprocal of the exposure inmeter candle seconds which is required to produce a double diffusereflection density of 0.2 density units above the sum of the base plusfog densities. As in the more conventional ASA system used to ratesilver halide films, the higher the LES number the faster thephotographic exposure speed of the film is.

Exposures are made on an Eastman l0] sensitometer with the lightconverted by the use of a 78AA Eastman Wratten Filter to equal meannoonday light (5500K).

In addition, the step tablet in the sensitometer is partly covered withstrips of Eastman filters No. 58 (green transmitting) and No. 29 (redtransmitting) so that a single exposure gives a measure of the responseof the film to white. green and red light.

The results with new compounds of this invention are Comparison compoundis 2-p-dimethylaminostyryl-4- methylthiazole methochloride.

What is claimed is:

1. 2-[p-Di(hydroxyethyl)aminostyryl] 5-methyl-3-hydroxyethylthiadiazolium chloride.

2. 2- [p-Di(hydroxyethyl)aminostyryl]-3,5- dimethylthiadiazoliumnitrate.

3. N-Hydroxyethyl-2-[p' di(hydroxyethyl)aminostyryl]-6-dimethylaminoquinolium bromide or chloride.

4. N-Hydroxyethyl-4-methyl-2-[p-di(hydroxyethyl)- aminostyryl]thiazoliumbromide or chloride.

5. A compound of the formula wherein y is a radical of a heterocyclicaromatic compound containing at least one quarternary nitrogen heteroatom and is selected from the group consisting of compounds of theformulae:

Formula I Rex" Fonnula II Formula III l RuX' A 1:1 R l RoX" Formula IVFormula V scribed herein.

1. 2-(P-DI(HYDROXYETHYL)AMINOSTYRYL)-5-METHYL-3HYDROXYETHYLTHIADIAZOLIUMCHLORIDE.
 2. 2-(p-Di(hydroxyethyl)aminostyryl)-3,5-dimethylthiadiazoliumnitrate. 3.N-Hydroxyethyl-2-(p-di(hydroxyethyl)aminostyryl)-6-dimethylaminoquinoliumbromide or chloride. 4.N-Hydroxyethyl-4-methyl-2-(p-di(hydroxyethyl)-aminostyryl)thiazoliumbromide or chloride.
 5. A compound of the formula